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1.
Opt Lett ; 49(11): 2882-2885, 2024 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-38824283

RESUMEN

We demonstrate mid-infrared time-domain optical coherence tomography (OCT) with an orientation-patterned GaP optical parametric oscillator. Instantaneous broadband mid-infrared spectra provide reduced scattering for OCT applications including cultural heritage, quality assurance, and security. B-scan calibrations performed across the wavelength tuning range show depth resolutions of 67 µm at 5.1 µm and 88 µm at 10.5 µm. Volumetric imaging inside a plastic bank card is demonstrated at 5.1 µm, with a 1 Hz A-scan rate that indicates the potential of stable broadband OPO sources to contribute to mid-infrared OCT.

2.
Opt Express ; 31(16): 25718-25723, 2023 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-37710451

RESUMEN

This Joint Issue of Optics Express and Optical Materials Express features 40 peer-reviewed articles written by authors who participated in the Advanced Solid State Lasers Conference, part of the Optica Laser Congress and Exhibition held in Barcelona, Spain from December 11-15, 2022. This review provides a brief summary of these articles covering the latest developments in laser host and nonlinear crystals, structured materials, fiber lasers and amplifiers, ultrafast mode-locked lasers and optical parametric amplifiers, frequency-doubled Raman lasers, vortex beams, and novel concepts in laser design.

3.
Opt Lett ; 48(11): 3055-3058, 2023 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-37262279

RESUMEN

Frequency combs present a unique tool for high-precision and rapid molecular spectroscopy. Difference frequency generation (DFG) of near-infrared sources is a common approach to generate passively stabilized mid-infrared combs. However, only little attention has been paid so far to precisely measure the coherence properties of such sources. Here, we investigate these using a Raman-soliton based DFG source driven by an Yb:fiber frequency comb. A heterodyne beat between the second harmonic of the phase-locked DFG comb near 4 µm and a 2 µm Tm:fiber frequency comb locked to the same optical reference is performed. Using this method, we measure the relative phase noise power spectral density of both combs. This results in a sub-Hz relative linewidth between the DFG comb and the Tm:fiber comb. We also introduce a new pump/seed delay locking mechanism based on interferometry for long-term stable intensity noise suppression.

4.
Opt Express ; 30(12): 20762-20766, 2022 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-36224813

RESUMEN

This joint issue of Optics Express and Optical Materials Express features 36 state-of-the art articles written by authors who participated in the international conference advanced solid state lasers held online from October 3-7, 2021. This review provides a summary of these articles covering a wide spectrum of topics around solid-state lasers from materials research to sources and from design innovation to applications.

5.
Opt Lett ; 47(5): 1259-1262, 2022 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-35230342

RESUMEN

A comparative analysis of AgGaSe2, GaSe, CdGeAs2, and Te for second harmonic generation (SHG) of a picosecond CO2 laser at intensities up to 50 GW/cm2 is presented. We demonstrate external energy conversion efficiency of >20% in AgGaSe2. Conversion efficiency >5% is measured in GaSe and CdGeAs2. Self-focusing and multifilamentation are found to severely limit the SHG process in CdGeAs2 and Te at such high fields. Demonstration of ≥150 MW SH pulses for a 10 µm picosecond pump, in combination with femtosecond CO2 laser development, will open new strong-field applications in the 4.5-5.5 µm range.

6.
Opt Lett ; 47(7): 1790-1793, 2022 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-35363736

RESUMEN

Broadband mid-infrared (MIR) molecular spectroscopy demands a bright and broadband light source in the molecular fingerprint region. To this end, intra-pulse difference frequency generation (IDFG) has shown excellent properties among various techniques. Although IDFG systems pumped with 1.5- or 2-µm ultrashort pulsed lasers have been extensively developed, few systems have been demonstrated with 1-µm lasers, which use bulky 100-W-class high-power Yb thin-disk lasers. In this work, we demonstrate a simple and robust approach of 1-µm-pumped broadband IDFG with a conventional mode-locked Yb-doped fiber laser. We first generate 3.3-W, 12.1-fs ultrashort pulses at 50 MHz by a simple combination of spectral broadening with a short single-mode fiber and pulse compression with chirped mirrors. Then, we use them for pumping a thin orientation-patterned gallium phosphide crystal, generating 1.2-mW broadband MIR pulses with the -20-dB bandwidth of 480 cm-1 in the fingerprint region (760-1240 cm-1, 8.1-13.1 µm). The 1-µm-based IDFG system allows for additional generations of ultrashort pulses in the ultraviolet and visible regions, enabling, for example, 50-MHz-level high-repetition-rate vibrational sum-frequency generation spectroscopy or pump-probe spectroscopy.

7.
Opt Lett ; 45(13): 3677-3680, 2020 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-32630928

RESUMEN

We demonstrate mid-infrared (MIR) frequency combs at 10 GHz repetition rate via intra-pulse difference-frequency generation (DFG) in quasi-phase-matched nonlinear media. Few-cycle pump pulses (≲15fs, 100 pJ) from a near-infrared electro-optic frequency comb are provided via nonlinear soliton-like compression in photonic-chip silicon-nitride waveguides. Subsequent intra-pulse DFG in periodically poled lithium niobate waveguides yields MIR frequency combs in the 3.1-4.8 µm region, while orientation-patterned gallium phosphide provides coverage across 7-11 µm. Cascaded second-order nonlinearities simultaneously provide access to the carrier-envelope-offset frequency of the pump source via in-line f-2f nonlinear interferometry. The high-repetition rate MIR frequency combs introduced here can be used for condensed phase spectroscopy and applications such as laser heterodyne radiometry.

8.
Opt Express ; 27(12): 16958-16965, 2019 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-31252913

RESUMEN

Optical rectification of near-infrared laser pulses generates broadband terahertz radiation in chalcopyrite crystals CdGeP2, ZnGeP2 and CdSiP2. The emission is characterized using linear-polarized excitation from 0.8 eV to 1.55 eV (1550 nm - 800 nm). All three crystals are (110)-cut and polished to 0.5 mm, thinner than the coherence length across most of the excitation photon energy range, such that they all produce a bandwidth ~2.5 THz when excited with ~100 fs pulses. It is found that CdGeP2 produced the strongest emission at telecoms wavelengths, while CdSiP2 is generally the strongest source. Pump-intensity dependence provides the nonlinear coefficients for each crystal.

9.
Opt Express ; 26(19): 25364-25369, 2018 Sep 17.
Artículo en Inglés | MEDLINE | ID: mdl-30469638

RESUMEN

We show that a variety of white powder samples, including painkillers, amino acids, stimulants and sugars are readily discriminated by diffuse reflectance infrared spectroscopy involving no preparation of the sample and no physical contact with it. Eleven powders were investigated by illuminating each sample with broadband coherent light in the 8-9-µm band from an OPGaP femtosecond optical parametric oscillator. The spectra of the scattered light were obtained using Fourier-transform spectroscopy. Similarities between different spectra were quantified using Pearson's correlation coefficient, confirming that spectral features in the 8-9-µm wavelength region were sufficient to discriminate between all eleven powders evaluated in the study, offering a route to simple and automated non-contact chemical detection.

10.
Opt Express ; 26(8): 10833-10841, 2018 Apr 16.
Artículo en Inglés | MEDLINE | ID: mdl-29716014

RESUMEN

Continuous-wave (cw) optical parametric oscillators (OPOs) are ideally suited for applications, for example high-resolution spectroscopy, that need coherent sources combining narrow-linewidth emission with good wavelength tunability. Here, we demonstrate for the first time cw OPOs based on a millimeter-sized whispering gallery resonator (WGR) made of cadmium silicon phosphide (CdSiP2). By employing a compact laser diode at 1.57-µm wavelength for pumping, a cw OPO with wavelength tunability from 2.3 µm to 5.1 µm is realized based on such a resonator. The oscillation thresholds are in the milliwatt range. The maximum total power conversion efficiency reaches more than 15%. The intrinsic quality factor at 1.57 µm is determined to be 3.5 × 106. This work suggests that CdSiP2 is a very promising alternative for constructing mid-infrared parametric devices.

11.
Opt Express ; 26(9): 11756-11763, 2018 Apr 30.
Artículo en Inglés | MEDLINE | ID: mdl-29716094

RESUMEN

We report the first fully fiberized difference frequency generation (DFG) source, delivering a broadly tunable idler in the 6 to 9 µm spectral range, using an orientation-patterned gallium phosphide (OP-GaP) crystals with different quasi-phase matching periods (QPM). The mid-infrared radiation (MIR) is obtained via mixing of the output of a graphene-based Er-doped fiber laser at 1.55 µm with coherent frequency-shifted solitons at 1.9 µm generated in a highly nonlinear fiber using the same seed. The presented setup is the first truly all-fiber, all-polarization maintaining, alignment-free DFG source reported so far. Its application to laser spectroscopy was demonstrated by the absorption spectrum measurement of ν4 band of methane in 7.5 - 8.3 µm spectral range. The system simplicity and compactness paves the way for applications in field-deployable optical frequency comb spectroscopy systems for gas sensing.

12.
Opt Express ; 26(15): 18975-18981, 2018 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-30114157

RESUMEN

Infrared spectroscopy in the spectral fingerprint region from 6.5 to 20 µm has been applied for decades to identify vapor- and condensed-phase chemicals with high confidence. By employing a unique broadband laser operating from 7.2- to 11.5-µm we show that, in this region, wavelength-dependent Mie-scattering effects substantially modulate the underlying chemical absorption signature, undermining the ability of conventional infrared absorption spectroscopy to identify aerosolized liquids and solids. In the aerosol studied, Mie theory predicts that the positions of spectroscopic features will blue-shift by up to 200 nm, and this behavior is confirmed by experiment, illustrating the critical importance of considering Mie contributions to aerosol spectroscopy in the mid infrared. By examining the spectroscopy of light scattered from an aerosol of the chemical diethyl phthalate, we demonstrate excellent agreement with a Mie-scattering model informed by direct measurements of the particle-size-distribution and complex refractive index.

13.
Opt Express ; 26(8): 9963-9971, 2018 Apr 16.
Artículo en Inglés | MEDLINE | ID: mdl-29715941

RESUMEN

We report a broadband mid-infrared frequency comb with three-optical-cycle pulse duration centered around 4.2 µm, via half-harmonic generation using orientation-patterned GaP (OP-GaP) with ~43% conversion efficiency. We experimentally compare performance of GaP with GaAs and lithium niobate as the nonlinear element, and show how properties of GaP at this wavelength lead to generation of the shortest pulses and the highest conversion efficiency. These results shed new light on half-harmonic generation of frequency combs, and pave the way for generation of short-pulse intrinsically-locked frequency combs at longer wavelengths in the mid-infrared with high conversion efficiencies.

14.
Opt Lett ; 43(1): 21, 2018 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-29328223

RESUMEN

This erratum reports a correction to the labeling of Figs. 2(b) and 3(b) in the original manuscript, Opt. Lett.42, 4756 (2017)OPLEDP0146-959210.1364/OL.42.004756.

15.
Opt Lett ; 43(5): 1099-1102, 2018 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-29489789

RESUMEN

We describe a compact and efficient mid-infrared (mid-IR) source based on zinc germanium phosphide (ZGP) and cadmium silicon phosphide (CSP) optical parametric oscillators (OPOs), operating in near degenerate condition, directly pumped by a 1.94 µm thulium (Tm)-doped yttrium-aluminum-perovskite (YAP) laser. The Tm:YAP laser is passively Q-switched by a chromium-doped zinc sulfide saturable absorber, and is operated to 4 W average power with a peak power of 29 kW. The laser emission was used to pump CSP and ZGP doubly resonant linear OPO cavities, generating a maximum 3.5-4.2 µm mid-IR emission of 2.5 W for CSP and 2.3 W for ZGP, with maximum optical conversion efficiencies of 65% and 58%, respectively, achieved for the two OPO crystals.

16.
Opt Express ; 25(15): 17411-17416, 2017 Jul 24.
Artículo en Inglés | MEDLINE | ID: mdl-28789233

RESUMEN

We generate over 60 mW of pulses with wavelengths from 6 to 11 micrometers by difference frequency mixing between erbium and thulium fiber amplifiers in orientation-patterned GaP with a photon conversion efficiency of 0.2. By stabilizing the repetition rate of the shared oscillator and adding a frequency shifter to one arm, the output becomes a frequency comb with tunable carrier envelope offset.

17.
Opt Lett ; 42(11): 2193-2196, 2017 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-28569879

RESUMEN

We report a tunable, single-pass, pulsed nanosecond difference-frequency generation (DFG) source based on the new semiconductor nonlinear material, orientation-patterned gallium phosphide (OP-GaP). The DFG source is realized by mixing the output signal of a nanosecond OPO tunable over 1723-1827 nm with the input pump pulses of the same OPO at 1064 nm in an OP-GaP crystal, resulting in tunable generation over 233 nm in the mid-infrared from 2548 to 2781 nm. Using a 40-mm-long crystal, we have produced ∼14 mW of average DFG output power at 2719 nm for a pump power of 5 W and signal power of 1 W at 80 kHz repetition rate. To the best of our knowledge, this is the first single-pass nanosecond DFG source based on OP-GaP. The DFG output beam has a TEM00 spatial mode profile and exhibits passive power stability better than 1.7% rms over 1.4 h at 2774 nm, compared to 1.6% and 0.1% rms for the signal and pump, respectively. The OP-GaP crystal is recorded to have a temperature acceptance bandwidth of 17.7°C.

18.
Opt Lett ; 42(22): 4756-4759, 2017 11 15.
Artículo en Inglés | MEDLINE | ID: mdl-29140361

RESUMEN

We report an octave-wide mid-IR spectrum (2.3-4.8 µm) obtained from a subharmonic optical parametric oscillator (OPO) based on a newly developed nonlinear crystal, orientation-patterned gallium phosphide (OP-GaP), which was synchronously pumped by a femtosecond 1560 nm fiber laser. We proved that the octave-wide output is in the form of a single frequency comb. The observed f-to-2f frequency beats, originating directly from the OPO, can be used for self-referencing and phase locking of the pump laser comb with no need for supercontinuum generation. With an average output power of ∼30 mW, this setup might be beneficial for a variety of spectroscopic applications in the mid-IR.

19.
Opt Lett ; 41(18): 4261-4, 2016 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-27628372

RESUMEN

We report a femtosecond optical parametric oscillator (OPO) based on the new semiconductor gain material orientation-patterned gallium phosphide (OP-GaP), which enables the production of high-repetition-rate femtosecond pulses spanning 5-12 µm with average powers in the few to tens of milliwatts range. This is the first example of a broadband OPO operating across the molecular fingerprint region, and we demonstrate its potential by conducting broadband Fourier-transform spectroscopy using water vapor and a polystyrene reference standard.

20.
Opt Lett ; 41(21): 5114-5117, 2016 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-27805704

RESUMEN

We report on the generation of coherent mid-infrared radiation around 5.85 µm by difference frequency generation (DFG) of a continuous-wave Nd:YAG laser at 1064 nm and a diode laser at 1301 nm in an orientation-patterned gallium phosphide (OP-GaP) crystal. We provide the first characterization of the linear, thermo-optic, and nonlinear properties of OP-GaP in a DFG configuration. Moreover, by comparing the experimental efficiency to Gaussian beam DFG theory, we derive an effective nonlinear coefficient d=17(3) pm/V for first-order quasi-phase-matched OP-GaP. The temperature and signal wavelength tuning curves are in qualitative agreement with theoretical modeling.

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